Weird add-on scenery problem...

I have Imagine Software's KDEN (which is awesome by the way) and many Simflyer's Intl. airport sceneries. I have the weirdest problem with KDEN and KLAX. Everytime I'm flying toward these airports my sim has to pause for about 30 seconds just to load the airport scenery in order for me to fly over it... I haven't seen this kind of behavior before. I'm talking a complete stand still in the air and what's really strange is may Hard Drive is not chugging away loading the scenery. You would normally see this kind of thing when scenery is loading.Does anyone know why this is a problem with just these two airports??? I haven't really tested all my other add-on's as of late so this could be a problem with other airport add-on